if you want to move the light source around to where your mouse is on the screen for instance
when you do set light x and set light y in bumpmapping
you can't :
set light x to mousex and
set light y to mousey
you have to:
set light x to (mousex-sprite.x)/sprite.width
and
set light y to (mousey-sprite.y)/sprite.height
or your lightsource will be in a totally different part of the world
I'm saying it'd be nice to just be able to put mousex and mousey and be done with it
OR, just be able to use the light object to automatically control the light source for bumpmaps